Calculate the sum of a nested list of int array, multiply by depth

Given a nested list of int array – calculate the sum of all the integers, while multiplying each number by its depth…

For example:

Here’s the depth sum of the nested list {1, {2, 3}}:

{1, {2, 3}} => 1*1 + 2*2 + 3*2 = 11

Here’s the depth sum of the nested list {1, {2, {3}}}:

{1, {2, {3}}} =>  1*1 + 2*2 + 3*3 = 14

First, lets define the data structure:

        public class NestedList
        {
            public NestedList(int val)
            {
                this.Val = val;
            }

            public int Val { private set; get; }
            public List<NestedList> nl;
        }

Here’s the test for {1, {2, {3, 4}}} =>  1*1 + 2*2 + 3*3 + 4*3 = 26

           var root = new NestedList(1);
            var i2 = new NestedList(2);
            var i3 = new NestedList(3);
            var i4 = new NestedList(4);

            root.nl = new List<NestedList> {i2};
            var list = new List<NestedList>();
            list.Add(i3);
            list.Add(i4);
            i2.nl = list;

            var results = root.DepthSum();
            Debug.Assert(results == 26);
 

Here’s the implementation

        public class NestedList
        {
            public NestedList(int val)
            {
                this.Val = val;
            }

            public int Val { private set; get; }
            public List<NestedList> nl;

            public bool IsNestedList()
            {
                return nl != null;
            }

            public int DepthSum()
            {
                return Calc(this, 1);
            }

            private static int Calc(NestedList nestedList, int dept)
            {
                int total = nestedList.Val * dept;
                if (nestedList.IsNestedList())
                {
                    int newDept = ++dept;
                    foreach (NestedList childNestedList in nestedList.nl)
                    {
                        total += Calc(childNestedList, newDept);
                    }
                }
                return total;
            }
        }